AS

Earthquakes II: Strain and Faults

Faults

  • faults: a large brittle fracture in a rock body
  • the point of origin for most earthquakes

Terminology

  • movement range along a break in a rock body is fractions of an inch to miles
    • fractures: fractions of inches to inch movements
    • faults: feet to mile movements
  • plate boundaries: contacts between tectonic plates

Normal Fault

  • blocks move away from each other
  • hanging wall block moves down relative to foot wall

Reverse (or Thrust) Fault

  • blocks move towards each other
  • hanging wall block moves up relative to foot wall

Strike-Slip Fault

  • motion is lateral (like traffic driving)
  • fault itself is vertical (no hanging wall or foot wall blocks)

Types of Strike-Slip Faults

  • left-lateral: movement relatively to the left
  • right-lateral: movement relatively to right